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Christmas was when they sent in the reinforcements. By then the regular troops were weary, though still stalwart, still brave. Some had lost limbs, others an eyeball. The soles of one guy’s feet kept peeling off. He was my favorite: a hippo. My mother patched his pads many times.

Every year the green recruits arrived, protruding from stockings or sprawled beneath the tree. Not only stuffed animals, but plastic and wooden animal figurines; books about animals, from stories to alphabets to encyclopedias; games and movies with animal heroes; clothing covered with images of animals.

Sure, there were dogs, cats and bunnies in our youthful menagerie; there were the animals of the barnyard, chickens and horses and pigs. But the wild ones, the ones my siblings and I only ever saw in zoos or photographs or on the screen — these were the ones we loved best. How fierce, how strange! They had claws or shells or impossibly long necks; they had spotted fur, manes like halos. They had soft pouches to carry their babies in. Tigers, bears, lions, elephants, monkeys, turtles, dolphins, koalas, giraffes: in those days, everything was animals. They made up the fiery pantheon of our imagination; through animals we explored the world. They were our army of play.

Children depend mightily on animals for comfort, inspiration, imagination and art. And parents have long recognized this. We read our children stories starring elephants and monkeys and bears to teach them about nobility, curiosity and courage, to warn them against selfishness and stubbornness. Without even knowing why, we believe that to learn how to be human — which we have many years to do, for human beings have longer childhoods than any other species, a feature that to biologists and philosophers alike is one of our race’s distinguishing characteristics — children must be surrounded by animal imagery.

True: when those children grow up, they no longer speak so often of their love for animals. As adults we deny or compartmentalize that fondness; we’re taught to privilege the love of our own kind above all others, and most of us accept that teaching.

Yet we have not forgotten the friends of our youth. Just open a magazine, look at a list of sports teams, at logos and billboards, at paintings and literature: the iconography of animals is quietly dominant. They’re with us still, in our dreams, in our jokes, in our built landscapes, in the stories we tell to make meaning of our lives.

Which makes me wonder: What of the children of the future? When the polar bears and penguins are gone, the gorillas and elephants and coral-reef clown fish like Nemo — what diverse and lovable army will be their close companions?

If the dinosaurs are any indication, there’s a place in our pantheon for the extinct. My son has a blue plushy allosaurus he calls Spot-Spot, with whom he often sleeps. Once, anxious about the sharp teeth on a T-Rex he’d seen in a picture book, he asked me whether he would ever meet a dinosaur. I said: No, darling. Dinosaurs last roamed the earth some 65 million years ago. People have never met the dinosaurs; we’ve only found their bones.

A future mother will most likely say, when asked if her child will meet a polar bear: No, dear. The polar bears lived a long time ago, when ice still floated on the Arctic seas. The last elephants trumpeted out their calls in Africa and India before you were even born. You have nothing to fear from a prowling lioness. Nothing at all. The army fell, she may think to herself. In the end, there were no more reinforcements to send.

Will Barbies and robots be enough for those future children? The hybrid monsters of fantasy video games, the fossil-based reconstructions? Maybe a few stray wild animals that were once our partners in this grandiose place will live on as collective memories, the bygone stars of screen and storybook, but they, too, must fade from the stores and eventually the pixels as time marches on.

On one hand, we’re a resilient civilization when it comes to tools and toys. We promptly fashion new ones as the old pass out of relevance. We will adapt — in terms of commodity creation, we’re masters of the universe.

On the other hand, resilience goes only so far. We’d do well not to rely on it as our primary survival strategy.

So those of us who are watching as the large mammals of the savanna, the colorful fish of the bleaching reefs, the seals and walruses of the melting poles are sacrificed to what could be the planet’s sixth mass species extinction: will we be the last, maybe the only, generation to grieve at their departure?

I know this much: the number of mourners will swell as the death toll rises and the creatures drop out of existence — even those who now are skeptics or believe stoutly in their own indifference will one day feel an ache of remorse, a pang of longing, where the great beasts once roamed. Where the bats flitted at night, where the bees alighted, where the flocks of birds darkened the sun. Those of us who knew of them will also know their absence. And the knowledge will be terrible.

But our grandchildren — that’s another question. Can you feel the loss of something you never knew in the first place?

For instance: I never knew the tall-grass prairies before they were razed, the vast herds of buffalo. I never knew the dodo or the passenger pigeon, the dusky seaside sparrow. For that matter, I never knew the American Indian tribes that winked out under the onslaught of the conquerors. At times, learning about these gone beings, cultures and languages, I experience a range of emotions related to their extermination. But what I feel is a proxy for loss — an idea of loss, an idea of something that can never now be known.

People simply have no history of living in a world without an abundance of other animals in the wild. We have no precedent for it. Such a world will be new to the children who come after us; indeed, it will be alien. This planet will no longer be our old, familiar home, but something completely other. And that will change the character, the aesthetics, the ideals of our descendants, growing up on a globe that has almost in the blink of an eye been purged of its ancient evolutionary richness.

If we don’t act fast enough to save the icons that make up our natural birthright — which is likely since, as the record too often shows, it’s our chronic bad habit to turn our faces away from unpleasant sights, to hem and haw and finally act too late, when tragedy has already struck — we’ll be sending those children into a starker, poorer land whose many possibilities have been eternally foreclosed.

Will the children easily turn their attention to an array of bright novelties, as fascinating to them as wild animals were to their forebears? Or will they, every now and then — after watching an old movie or reading an old book and glimpsing the marvelous strangeness and beauty of what once lived here with us — imagine those sad multitudes with dragging wings and drooping tails and make a childish wish: Can’t you come back? Come back, come back! Come back to us, you great, dead creatures of the earth.